How about the barbell squat in the SDI’s office...
They had a barbell, (two huge coffee cans cemented to a bar), you'd have to bend over at the waist and pick it up, with your back against the wall, slide down the wall into the squat position while holding the barbell straight out
(about fifty pounds) and maintain that position until he says UP! You repeat on command, and don't dare lower the barbell.
I remember the coffee can barbells but never had the pleasure of using them.
Another favorite back in the day at PI was to hold the M1 Garand at arms length, using just the thumb and curled forefinger of each hand to grasp it by the stacking swivel.
And you knew what was in store if you dropped your weapon in front of the DI.